In order to analyze the effect of aluminum fiber contents on the underwater explosion performance of RDX‐based explosives, the pressure‐time curves of composite explosives with different aluminum fiber contents are measured by underwater explosion experiments. Peak pressure, impulse, shock energy, and bubble energy were obtained by analyzing the curves. The results show that the peak pressures of composite explosives decrease with increasing aluminum fiber contents. The shock impulse of the 30 % aluminum fiber composite explosive is the highest in all composite explosives. The effects of the 20 % and 40 % composite explosives are nearly equal to that of the 30 % explosive, and the different values of shock impulse among them do not exceed 5 %. The specific shock energy of the 20 % aluminum fiber composite explosive is the highest in all composite explosives. The bubble energy and explosion energy of composite explosives increase with increasing aluminum fiber contents.

Experiments were conducted to study the underwater explosion performance of titanium hydride/RDXbased (TiH 2 /RDX) composite explosive. Cylinder charges with different TiH 2 particle sizes and contents were prepared and tested. Explosion parameters like peak overpressure, impulse, shock energy, and bubble energy were analyzed. It was notable that underwater explosion performance of TiH 2 /RDX composite explosive was promoted by addition of small particle size TiH 2 (D 50 = 0.96 mm), in which case increasing TiH 2 content also showed a favorable effect. The maximum increments of specific initial shock energy, bubble energy, and total energy were 10.5%, 6.4%, and 7.1% respectively. However, with bigger TiH 2 particle sizes (D 50 = 20.78 mm, D 50 = 136.74 mm), the explosion parameters and the TiH 2 content showed a negative relationship, which reveals that TiH 2 particle size plays an important role in determining the reactivity of TiH 2 . Meanwhile, the interaction between TiH 2 particle size and content was significant.

Two typical binary metal hydrides, TiH2 and MgH2 were introduced into the RDX based explosive composites. Charges with different contents of metal hydride were evaluated through underwater explosion. Composite with 10 % MgH2 exhibited the best shockwave parameters, peak overpressure, specific impulse and specific shock energy of which promoted by 5.7 %, 7.0 % and 8.4 % respectively. Whereas, the specific bubble energy of composite with 10 % TiH2 showed the maximum enhancement of 5.5 %, and density specific energy of which increased significantly attributed to the large density of TiH2. Meanwhile, a 2‐year ambient storage test of metal hydride reactants and RDX‐metal hydride explosive composites was conducted to evaluate the safety and stability. X‐ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA) were then conducted to analyze the aged samples. Results revealed that TiH2 and its explosive composites showed an excellent storage stability due to the formation of thin TiO2 film. Whereas, mass fraction of Mg(OH)2 was found increasing with time in both MgH2 and its explosive composite, of which hydrolysis of MgH2 was the main mechanism. Moreover, Mg was found in aged MgH2 powder as a result of decomposition. The mechanical strength of aged charges of RDX based MgH2 explosive composite also degraded significantly ascribed to the released hydrogen.

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The cover picture shows the RDX based MgH2 (MHR‐10) and TiH2 (THR‐10) explosive charges aging in the ambient environment. During the 2‐year storage tests, the weights and sizes of MHR‐10 charges were increased significantly because of the hydrolysis and decomposition of MgH2 . Micro‐cracks and defects due to hydrogen generation resulted in a remarkably strength loss of the MHR‐10 charges. Whereas, further degradation of TiH2 was prevented by the formation of the external TiO2 film, which ensured the compatibility and stability of the THR‐10 explosive composites. Though the energy performance of the studied fresh RDX based metal hydride explosives was promoted (illustrated by underwater explosion tests), the storage stability of MHR‐10 was unsatisfied for practical application. Details are discussed in the article by Bing Xue et al. on page 671 ff.